1. Field of Invention
The present invention relates to a technique of eliminating static electricity, and more particularly to an electrostatic discharge guide using metal sputtering process and modifying plastic case.
2. Related Art
In order to meet demands of various appearance designs, different materials, such as metal or plastics, are generally adopted to fabricate the case of an electronic device. In addition, as for the design of fabricating the housing of an electronic device with metal, usually the metal housing is directly electrically connected to a ground terminal of an electronic component inside the device, so as to successfully release the static electricity from a ground terminal of the electronic device. The above manner may not cause any problem in non-portable electronic devices. However, when the same manner is applied to a portable electronic device, due to the current leakage of the electronic component, the user may feel an electric shock when directly contacting the housing of the electronic device. Further, the electrostatic protection should be considered during the design of a portable electronic device. That is, under a particular electrostatic shock (impact) test, the portable electronic device still works normally. Therefore, in the above design (the metal case of the portable electronic device is electrically connected to a ground area of the electronic component), during the electrostatic test, after striking on the metal case, a static electricity of 8 KV is immediately guided to the ground terminal of the electronic component. In this manner, a transient high voltage will directly impact on the electronic component, and thus the electronic component needs to be designed with more protections.
In order to solve the problem of current leakage of the electronic component, in some methods, a plastic case is added between the metal case and the electronic component, so as to electrically insulate the two. Although the above method prevents the user from being electrically shocked by the leakage current of the electronic component, the metal case does not have any ground mechanism, such that the metal case accumulates static electricity when held by the user for a long time or obtains an electrostatic value for absorbing the static electricity from the nature. At this time, when the user again contacts the electronic device, a potential difference exists between the electrostatic value of the user and the electrostatic value of the metal case, and thus the user may feel an electric shock.